- Add optional nulls_distinct arg to UniqueConstraint, which maps to …

…NULLS NOT DISTINCT in SQL

- See https://code.djangoproject.com/ticket/34701
- Also https://www.postgresql.org/docs/current/indexes-unique.html

django-stubs/db/models/constraints.pyi

@@ -61,4 +61,5 @@ class UniqueConstraint(BaseConstraint):
         include: str | Sequence[str] | None = ...,
         opclasses: Sequence[str] = ...,
         violation_error_message: str | None = ...,
+        nulls_distinct: bool | None = ...,
     ) -> None: ...